Transmitter adjusting system



P L A. PREISMAN TRANSMITTER ADJUSTING SYSTEM Filed Jan. 8, 1945 2Sheets-Sheet l TUNING IIYBICHTOR CIRCUITS 1.5 I mac/mm C lRCl/IT vFREQUENCY scam/me RECEIVE? 5 WE EP GENE/2H TOR HND CONTROL FIJI-5EHER/8'5 INVENTOR.

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TRANSMITTER ADJUSTING SYSTEM Filed Jan. 8, 1943 2 Sheets-Sheet 2HMPLJTUDE TIME IN VEN TOR. 4L BE f? T PRE/SMHN HIM ATTORNEY PatentedApr. 1, i947 2,418,139 TRANSMITTER ADJUSTING SYSTEM Albert Preisman,

Federal Telephone Flushing, N. Y., assignor to d Radio Corporation,

Newark, N. J., a corporation of Delaware Application January 8, 1943,Serial No. 471,653

9 Claims.

This invention relates to radio circuits and more particularly tocircuit tuning systems for tuning a circuit to a desired frequency.

In the transmission of jamming signals it is desirable to provide meansfor scanning over a frequency band in a receiver in order to determinethe operating frequency of an enemy transmitting station so that jammingsignals may be transmitted at the enemy frequency.

The tuning of the jamming transmitter to the enemy frequency may beaccomplished by applying the transmitted jamming signals to a commoncathode ray indicator together with the received enemy signal. The twoindications may be made to coincide on the common indicator screen. Asystem of this type is described in the copending application of E.Labin, Serial No. e51,- 302, filed July 17, 1942.

This method is not very sensitive since the frequency of the receiver iscontinuously changed and the incoming signals are only momentarilypresent. Accordingly, it has been proposed to accomplish the tuning ofthe transmitter more precisely to the received signal frequency byinterrupting the frequency scanning for a period and manually tuningthis receiver and transmitter until maximum indications of the receivedand the jamming transmission appear on the cathode ray screen. Thecathode ray beam scanning sweep may be maintained during this tuning tospread the indications over the face of the tube to make the observationeasier.

Alternatively a separate receiver may be used in conjunction with thescanning receiver for the purpose of close transmitter tuning.

It is an object of my invention to provide an indicator for quiteprecisely indicating the frequency of a signal received on acontinuously cyclically tuned receiver without interrupting the cycle ofsaid tuning.

It is a further object of my invention to provide a system wherein atransmitting station may be tuned to the frequency of a particularreceived signal.

It is a still further object of my invention to provide a system givingindications permitting the tuning of a transmitter to a frequencycorresponding to a signal received on a cyclically tuned receiverwithout interrupting the cycle of said tuning.

According to my invention ,a frequency scanning receiver and cathode rayindicator are provided as in the previously proposed systems. A separatepulse of very short duration is produced with a period synchronized withthe cathode ray scanning cycle. The short pulse is applied to switchoutput energy of the receiver momentarily to an auxiliary indicator toreproduce on the screen of this auxiliary indicator the pulses receivedduring this interval. Means is provided for adjusting the time phaseposition of this pulse with respect to the frequency position of thescanning receiver so that any point on the fre quency scale of theprincipal indicator may be chosen for reproduction on the auxiliaryindicator.

Thus, the particular point on the scale corresponding to a selectedfrequency may be chosen for reproduction on the auxiliary screen. If thereceiver system is combined with jamming the jamming transmitter maythen be adjusted to produce a maximum indication on this auxiliaryindicator. Then it is clear that the transmitter is properly tuned tointerfere with the selected frequency.

A better understanding of my invention may be had from the particulardescription thereof made with referenc to the accompanying drawings, inwhich:

Fig. 1 is ,a block diagram of a circuit embodying the features of myinvention;

Fig. 2 is a circuit diagram of certain novel elements shown in blockeddiagram in Fig. l; and

Fig. 3 is a set of curves which serve to explain the operation of thesystem.

In Fig. 1, H! represents a receiver which is continuously scanned over aband of frequencies by any desirable means such as motor H. A jammingtransmitter I2 is provided for transmitting signals to jam enemycommunication. In order to detect the presence of enemy transmissions,there is provided in the output of receiver in the cathode ray indicatorIS, the sweep frequency of which is generated in the sweep generator andpulse control means I4. Motor ll serves to operate sweep generator M insynchronized relation with the frequency scanning of receiver lil.Circuit 14 also serves to produce control impulses which operateblocking circuit I5. Blocking circuit it: may be, for example, amultivibrator used to alternately apply blocking potentials to thetransmitter and the receiver preferably arranged so that the transmitteris in operation for a longer period than the receiver. The blockingpotentials applied to the scanning receiver render it insensitive to lowamplitude signals such as those received from distant transmitters. Thejamming signals from transmitter !2, however, are sufliciently strong toovercome th blocking bias in receiver It so that indiscanning receiverI0.

'entiating circuit the pulses produced in In operation the systemcations of the jamming transmitter appear also on indicator l3. Fromthese the frequency of the transmitter may be determined. A manualtuning control I6 is provided on jamming transmitter I2 so that thistransmitter may be tuned to any desired frequency.

The transmitter-receiver circuit so far described may, for example, beof the type more fully described in the aforementioned patentapplication of E. Labin, Serial No. 451,302. With this system, however,the indications on the screen of I3 are relatively small and for thisreason precise tuning of the transmitter to the enemy received signal isvery difficult. 'In the E. Labin application a method of more precisetuning of the transmitter is described but this necessitatesinterruption of the scanning for the period in which the tuning is beingmade so that the jamming and received signals may be expanded on theoscillograph I 3.

In the circuit of Fig. 1, I provide a system perimitting the tuning ofthe transmitter to any one of the frequencies indicated by the receivedpulses on indicator I3 without interruption of the continuous tuning orscanning of receiver I0. To

accomplish this, a pair of tuning indicator circuits H are connected inthe output of frequency These indicator circuits are each biased so thatnormally no signal received on ID or transmitted energy from I2 received on this circuit will pass. Blocking circuit I is connected to thetuning indicator and alternately reduces the bias of the respectivereceived signal and jamming transmitter indicator circuits towardcut-off. This bias from the blocking jcircuit is not sufilcient torender the circuits conductive.

A multivibrator I8 synchronized with the sweep frequencies generated inI4 is provided. This multivibrator is designed to maintain the rhythm ofthe sweep frequency but is made adjustable,

as indicated by knob 2|, to vary the width of its output waves. Thesquare wave pulses produced in multivibrator l 8 are passed through thediiferresponding to the leading and trailing edges of multivibrator I8.These shaped pulses are then applied to the tuning indicator circuits I!in additive relation to the potentials from the blocking circuit. Thepulses I superposed on the potentials from the blocking bias of thetuning indicator just below cut-01f. Accordas energy is applied to thetuning indicator circuit I! from the output of receiver I 0, the biascontrol from blocking circuit I5 and dif circuits reduce the circuits toa point ferentiating circuit I9 will be alternately operative so thatthe particular received signal and the jamming transmitter signal may bepassed to auxiliary indicator 20 provided the bias potentials areadjusted properly in time to coincide with the frequency at which thereceived signal and the jamming transmitter are operated.

serves to switch the received energy to the tuning indicator circuitmomentarily for a period determined by the length of the pulse producedin be made very narrow in I9. This pulse should order that a goodfrequency selection be obtained. If the time of occurrence of thismomentary sensitizing effect is adjusted to coincide with the time thatthe re- ;ceiver frequency is at a position corresponding to a selectedstation, this station will be indicated on 29., To make this adjustmentit is only necessary to control multivibrator I8 by means 2| I9 toproduce shaped pulses corconnected to the indicator until a maximumindication is produced in indicator 20. Control knob 2| may becalibrated to show the frequency of the received signals. It is thenonly necessary to tune the jamming transmitter by means of control knobI6 until a maximum indication of this jamming transmitter is alsoindicated. Then the jamming transmitter is quite precisely tuned to thedesired received frequency.

A clearer understanding of the operation of tuning indicator I! may behad by reference to the circuit diagram shown in Fig. 2 explained inconnection with the curves of Fig. 3.

Curve A of Fig. 3 illustrates the scanning cycle produced in sweepgenerator it of Fig. 1. This scanning cycle is such that indicator I3 isscanned at regularly repeated intervals by a clipped sawtooth wave, theintermediate portions being substantially the same length as the activeportion of the sawtooth wave. It is clear that this suppressed sawtoothWave form is not.

necessary but is preferable in the system described. In any event thesawtooth wave is made to scan the beam in one direction while thereceiver frequency changes in a particular direction. At the same timecircuit I4 serves to produce control pulses generally of the typeindicated by curve B of Fig. 3. These pulses applied to blocking circuitI5 produce a square output wave of the form generally shown in curve C.The output waves may be limited to a constant level indicated at 6D tomake them truly square wave in form. During the periods indicated by 6|the receiver is unblocked for the reception of ordinary signals and thetransmitter is blocked. During the longer period 62 the receiver isblocked for ordinary signals and the transmitter is unblocked. One ofthe scanning cycles of the receiver occurs during this period 62 andsince the jamming signals are of sufiicient amplitude to pass throughthe blocked receiver, an indication of this jamming transmitter tuningwill appear on indicator I 3.

Multivibrator I8, Fig. 2, may comprise vacuum tubes VI and V2, arrangedin the form employing a common cathode resistor 3|. Any other desiredform of multivibrator may be used. The sharp pulse of curve B is appliedas a synchronizing voltage to the grid of VI, while the tube V2 may haveits bias varied by means of the variable connection of high resistance34, on low resistance 33, connected across the bias battery 35. Aby-pass condenser 36 may be connected across the connection to ground ifdesired. This adjustment of bias permits the width of the wave to bevaried. The synchronizing pulse establishes the timing of edge 10 ofwave D, Fig, 3. The variation in bias causes a variation in the otheredge of the wave so that it may take adjustable positions such as, forexample, II, TIA, 7 IB.

By difierentiating the wave a series of pulses are obtained as shown incurve E. Pulses 8| are fixed in position and correspond to edge 70 ofcurve D. Pulse indications 80, A and 80B represent various positionsthat the negative pulse may assume with different adjustments of thebias.

The tuning indicator circuits are shown at I! shown at 20. Circuits I!consist of two tubes V3 and V4, each provided with cathodes '40, 50,anode 4!, 5| and and 5 5, respectively.

while the circuit of tube V4 is referred to as the I? transmitterindicator circuit. Normally both of these tubes are biased negatively toa poin considerably below cut-off. Energy from blocking circuit isapplied alternately Ito grids M and 54 bringing the transmitterindicator circuit and the receiver indicator circuits alternately to apoint much nearer the operative condition. The client of thisapplication and the operation of the blocking circuits generally may bemore clearly seen by reference to curve F, Fig. 3, in conjunction withFig. 2. The bias point for the two circuits is indicated by line eaimpulses applied on grids 44 and 54 raise this potential to a highervalue as shown at 9| for the receiver indicator circuit and 92 for thetransmitter indicator circuit. The pulses derived from differentiatingcircuit H; are then applied in the same polarity to grids 43, 53 oftubes V3 and V4 as indicated. These pulses add to the bias provided bythe blocking circuit and bring tubes V3 and Vi to a point just belowcut-off as indicated by the superposed pulses 93 of curve F. Forconvenience of illustration curve F is shown as a wave form. However, itis to be understood that the potentials applied to the receiverindicator, and to the transmitter indicator are both positive, beingderived from opposite output ends of the blocking device as described inthe aforementioned application of E. Labin. The position of thesesuperposed pulses 93 may be varied to positions corresponding to pulses80A, 80B of curve E, as indicated at 93a, 53b. Thus, the tuningindicator 20 is rendered responsive to received signals for a shortperiod determined by the width of pulses '93, which period may bedisplaced over the entire tuning cycle of the frequency scanningreceiver ID. If any received signals are applied to grid 42 of tube V3at the time when the peak potential 93 is present, there will be anoutput from the tube which will serve to produce an indication of meter45. By adjusting the width of the square pulses of curve D the positionof pulses 93 may be adjusted to coincide precisely with the selectedreceived signal at which time a maximum reading will be obtained onmeter 45.

If after this adjustment has been made the transmitter tuning iscontrolled until the energy therefrom is applied to grid 52 of tube V4simultaneously with the application of peak potential 93, then anindication will also be produced on meter 55 of indicator 20. When thecondition of maximum response has been achieved, the transmitter isproperly tuned to the jamming station.

It is clear that other forms of indicators may be provided if desiredbut in general the pulses 93 are of such short duration that a verysensitive indicator must be provided. It is therefore preferable to usesimple meters rather than more complex cathode ray analyzing apparatus.

It is to be understood that the received signal indicator such asrepresented to be V3 and its associated circuits may be used forprecisely determining the location of a signal relative to a frequencyband independently of the jamming transmitter arrangement. In this caseprovision for alternate operation of the tuning indicator circuit tocorrespond with the transmitter operation is not necessary and pulsessuch as shown at 93 may be used without the added impulses 9| to bringthe bias to the point just below cut-off. It it also clear that thearrangement herein described may be used wherever it is desired toadjust two tuned circuits to the same frequency whether or not thesignals are" derived from a radio receiver or from some other source.With the circuit in accordance with my invention, it is possible to timetwo systems to exactly the same frequency even though the actualoperating frequency of neither circuit is known.

While I have described my invention as applied to a particulartransmitter receiver system, it is clear that the principles of myinvention are much broader than this specific disclosure and may beapplied to many problems a will occur readily to those skilled in theart.

What is claimed is:

l. A circuit for indicating the frequency of a selected applied signalcomprising a signal receiver for said applied signal, means forcontinuously tuning said receiver over a band of frequencies, meansoperative in synchronism with said means for continuously tuning saidreceiver for producing control pulses, a tuning indication circuitcoupled to the output of said receiver but normally nonresponsive toreceived signals, means for applying said control pulses to said tuningindicator for rendering it momentarily responsive to applied signals,and means for adjusting the position of said control pulse with respectto said band of frequencies to a position corresponding to said selectedapplied signal.

2. A method of indicating on an indicator the frequency of a selectedapplied signal among several applied signals indicated on a receiverwhich is continuously cyclically tuned over a band of frequencies,without interrupting the continuous tuning, comprising producing pulsesin synchronism with said continuous tuning, causing said pulses to applyindicator potentials to said indicator in response to said pulses, andadjusting said pulse position with respect to the cycle of said tuningto control the position of application of said indicator potentials withrespect to said selected applied signal.

3. A circuit for indicating the frequency of a selected radio stationindicated on a receiver provided with means for continuously tuning saidreceiver over a band of frequencies which comprises, means operative insynchronism with said means for continuously tuning said receiver forproducing control pulses, a tuning indication circuit coupled totheoutput of said receiver but normally nonresponsive to received signals,means for applying said control pulses to said tuning indicator forrendering it momentarily responsive to received signals, and means foradjusting the position of said control pulse with respect to said bandof frequencies to a. position corresponding to said selected station.

4. A method of indicating on an indicator the frequency of a selectedradio station from among several stations indicated by signals receivedon a receiver which is continuously cyclically tuned over a band offrequencies, without interrupting the continuous tuning, comprisingproducing pulses in synchronism with said continuous tuning, causingsaid pulses to apply indicator potentials to said indicator in responseto said pulses, and adjusting said pulse position with respect to thecycle of said tuning to control the position of application of saidindicator potentials with respect to a received signal,

5. A circuit for indicating the frequency of a selected received radiosignal among several signals indicated in the output of a radioreceiver,

said receiver being continuously cyclically tuned over a band offrequencies for indicating the frequency of said received signals andthe tuning of a transmitter operated alternately With said receiver,comprising indicator means in the output of said receiver for indicatingsaid received signals and said transmitter tuning, means for normallymaintaining said indicator means in nonresponsive condition, means forproducing control pulse potentials to synchronize with said cyclicaltuning for rendering said indicator means responsive to signals fromsaid receiver and means controlled with said alternate operation of saidreceiver and transmitter for alternately applying said pulse potentialsto said indicators for rendering said indicators responsive to saidsignals from said receiver.

6. A circuit according to claim 3, further comprising means foradjusting the position of said pulses relative to said tuning cycle toposition said pulses at a point corresponding to the frequency of saidselected received radio signal.

7. A circuit according to claim 3, further comprising means foradjusting the position of said pulses relative to said tuning cycle toposition said pulses at a point corresponding to the frequency of saidselected received radio signal, and means for tuning said transmitter toproduce maximum indication at the pulse position corresponding to saidpoint.

8. In a radio receiver provided with means for cyclically scanning thefrequency of said receiver over a predetermined band of frequencies,Whereby said receiver responds to received signals within saidpredetermined band and means for indicating said response to show theapproximate frequency of said received signals, means for more preciselyindicating the frequency of a selected one of said received signalscomprising a tuning indicator circuit for responding to receivedsignals,means biasing said tuning indicator circuit to normally render itnonresponsive to received signal, means for producing control pulses ofa given polarity in synchronism with said scanning, means for applyingsaid pulses to said tuning indicator circuits to reduce said bias tosuch a level that incoming received signals will operate its circuit,means for controlling the position of said pulses to position them wtihrespect to said scanning cycle for selecting a received signal of aparticular frequency and means in the output of said tuning circuit forproviding an indication of maximum response in said circuit.

9. In a radio receiver provided with means for cyclically scanning thefrequency of said receiver over a predetermined band of frequencies, atransmitter for transmitting energy at a tunable frequency, blockingmeans for alternately blocking operation of said transmitter andreceiver, the blocking of said receiver being insufliciently complete toprevent reception of said transmitted energy whereby said receiverresponds to received signals within said predetermined band and to saidtransmitted energy, and means for indicating said response to show theapproximate frequency of said received signals and said transmittedenergy; means for more precisely indicating the frequency of a selectedone of said received signals and said transmitted energy comprisingtuning indicator circuits for responding respectively to receivedsignals and to said transmitted energy, means biasing said tuningindicator circuits to normally render them nonresponsive to receivedsignals and said energy, means for coupling said blocking circuit tosaid tuning indicator circuits to partly overcome said bias during thereceiving and transmitting cycles respectively, means for producingcontrol pulses of a given polarity in synchronism with said scanning,means for applying said pulses to said tuning indicator circuits inadditive relation to the energy from said blocking circuit to reducesaid bias to such a level that incoming received signals and saidtransmitted energy will operate their respective tuning circuits, meansfor controlling the position of said pulses to position them withrespect to said scanning cycle for selecting a re-- ceived signal of aparticular frequency and means in the outputs of said tuning circuitsfor providing an indication of maximum response in said respectivecircuits.

ALBERT PREISMAN.

